This invention relates to a semi-moist pet food and more particularly to a semi-moist pet food utilizing a vegetable protein, starch or flour, and at least one substantially neutral chelating agent in combination to replace at least part of the casein salt component of the semi-moist pet food.
Within the class of foods known as pet foods, there are three basic subdivision: (1) dry pet food containing low moistures; (2) semi-moist pet food containing medium moistures; and (3) moist pet foods containing high moistures. The moisture content is determined by considering both the water present in the final product and the water combined with the various components that make up the final product. In general, the dry pet food tends to be the most stable and requires to special handling or packaging upon distribution. The semi-moist pet food tends to be less stable than the dry pet food and requires a more careful packaging system. However, the semi-moist pet food requires no refrigerated storage, and tends to be microbiologically and bacteriologically stable due to the presence of various stabilizing agents. The moist pet food requires stringent canning conditions. In fact, the moist pet food is canned and sterilized by retorting in the usual manner. When the can is opened, the pet food not consumed must be refrigerated to preserve it. Thus, it may be seen that -- after a pet food is opened and partially used -- the dry pet food is the most stable pet food; the semi-moist of medium stability and the moist of lowest stability. When considering palatability, generally speaking the moist pet food tends to be the most palatable and the dry pet food tends to be the least palatable. The semi-moist pet food falls somewhere in between the moist and the dry pet food as to palatability. It follows that both as to palatability and stability the semi-moist pet food ranks in between the dry and the moist pet food. This ranking permits the semi-moist pet food to provide both shelf stability and palatability. In other words, a pet owner using a semi-moist pet food has fewer problems storing a pet food which his pet will eat.
The advantages of a semi-moist pet food thus become obvious. In semi-moist pet foods and other processed foods, casein derivatives such as sodium caseinate provide a highly suitable material. This material can be classified as a thermoplastic protein, is a good moisture and meat binder, and can be the basis of a good extrudable material. Furthermore, this material has such a high protein content, that it is used as a standard for determining or measuring protein quality of other protein-containing materials. So, in addition to the processing advantages of using caseinate, there is also a nutritional advantage due to the protein provided thereby. It thus becomes obvious why this material is so widely used in the food processing art and especially in the pet food art. However, the pricing of casein derivatives such as soidum caseinate are very high due to the economic conditions associated with milk processing. This price is so high, that it is economically unfeasible to use the amounts of caseinate in pet foods that are currently being used or desired. It follows that it is desirable to develop a replacement for at least some of the casein in order to bring down final product cost.
The unique qualities of casein salts -- such as for example sodium, calcium, magnesium, ammonium, and potassium caseinate -- render them difficult to replace. Not only must the replacement provide protein and processability, the appearance and flavor of the product must be substantially maintained. For example, it is customary to extrude semi-moist pet foods. Specifically, semi-moist pet foods containing caseinate derivatives are easily extrudable. It follows that the replacement for this component should also provide easy extrudability for the product in order to avoid substantial changes in machinery and manufacturing equipment. The protein level of the replacement must remain high and the palatability of the product containing the replacement must remain substantially the same.
Replacing a part of a casein derivative, such as sodium caseinate, creates further problems. Dilutions of the sodium caseinate concentration in a pet food tend to reduce the overall effect of the sodium caseinate. As the concentration of sodium caseinate is decreased and replaced by another component, the solubility, thermal properties, and elastic and structure forming properties contributed by caseinates to the dough are reduced. Thus, even partial replacement of sodium caseinate causes problems due to the fact that the effect of the remaining sodium caseinate is reduced.
Thus it may be seen that while costs have made casein derivatives an unacceptable component of a pet food, it is nevertheless difficult to replace a product component providing so many advantages.